Throughout computer systems, individual counters are used to keep track of time of day for trace time stamps.
Event tracing and logging is one of the most important tools used to debug computer designs, and one of the most useful pieces of information in each entry is a time stamp. Time stamps obviously point out time delays in the system, but they are also very valuable in coordinating multiple trace entries generated my multiple processes in the system.
Systems are often designed with multiple entities in different parts of the system generating independent trace entries, and processes often span multiple entities. The trace data is usually gathered by a single processor that has access to a Time of Day (TOD) register. However, the time stamps provided in trace entries provided by remote (to the processor) entities may have only a loose relationship to the TOD.